The invention relates to an apparatus for threshing legumes, comprising a frame which is movable over a ground surface, in which frame a drum which is rotatable about its at least substantially horizontally oriented axis of rotation is mounted, the drum surface of which is provided with one or more openings, wherein a main threshing element is disposed within the drum, which main threshing element is rotatable about its longitudinal axis extending at least substantially parallel to the axis of rotation of the drum; wherein at least one auxiliary threshing element is disposed within the drum, which auxiliary threshing element is rotatable about its longitudinal axis extending at least substantially parallel to the axis of rotation of the drum, and wherein additional conveying means are disposed within the drum for conveying the legumes to be threshed through the drum.
A threshing apparatus as referred to in the introduction is known, for example from U.S. Pat. No. 5,372,547. In said known apparatus, the legumes or pods are crushed by the threshing elements, so that the pods are opened and a threshing mixture consisting of seeds and shells/pods is obtained. This mixture is to be carried out of the drum for further processing. In said US patent, the flow of product through the threshing drum is realised by additional conveying means disposed within the drum. The flow of the threshing mixture is now separated from the main threshing element, for which threshing element a simpler construction not comprising any specific adjustable or fixed threshing blades may now be used.
During operation, a component of motion not only in radial direction but also in longitudinal direction is imparted to the threshing mixture. The latter component of motion leads to a steady movement of the threshing mixture from one end of the threshing drum to the other. One drawback of the threshing apparatus described in said US patent is the irregular flow of the threshing mixture through the threshing drum in situations in which the threshing apparatus includes an angle with the horizontal or the ground surface. A horizontal position of the threshing drum is required—even in situations in which the ground surface is not flat—in order to obtain a proper flow of the threshing mixture through the threshing apparatus.
To solve this problem, Dutch patent application No. NL-89/01658 (in the name of the present applicant) uses a complex stabilisation system, which places the entire threshing apparatus, or at least the threshing drum, in a substantially horizontal orientation with respect to the ground surface, even in situations in which the ground surface (for example a field) is not flat but exhibits a slope. In the apparatus according to NL-89/01658, the flow of the threshing mixture is not realised by additional conveying means, as in U.S. Pat. No. 1-5,372,547, but it is largely determined by the angle at which the threshing blades extend with respect to the main threshing element.
In a very complex embodiment it is possible to adjust said angle so as to regulate the flow in this manner. As a result, it is no longer possible, however, or only to a limited extent, to actively adapt the angle of the threshing drum by using variable angles of inclination when the apparatus is moving over a sloping ground surface.